Lecture 7 - Debugging and Profiling

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Lecture 7 - Debugging and Profiling

Laura Gheorghe, Petre Eftime 2

Android logging framework

Logger kernel module 4 separate buffers in memory

Main for application messages Events for system events Radio for radio-related messages System for low-level system debug messages

Pseudo-devices in /dev/log Main, radio and system - 64KB buffers, free-form text Event - 256KB buffer, binary format


Message Structure

Priority - severity Verbose, debug, info, warning, error, fatal

Tag identifies the component generating the message Logcat and DDMS can filter log messages based on the tag

Message: actual log text Buffers are small => do not generate long messages


Native Logging API

Exposed through android/log.h #include <android/log.h> Android.mk dynamically link native code to log library

LOCAL_LDLIBS += −llog Before include $(BUILD_SHARED_LIBRARY)


API

__android_log_write Generate a simple string message Params: priority, tag, message

__android_log_print Generate formatted string (like printf) Params: priority, tag, string format, other params

__android_log_write(ANDROID_LOG_WARN, "my_native_code","Warning message!");

__android_log_print(ANDROID_LOG_ERROR,"my_native_code", "Errno =%d", errno);


API __android_log_vprint

Additional parameters as va_list

__android_log_assert Assertion failures Priority is not specified, always fatal

SIGTRAP to process - debugger inspection

void log_verbose(const char* format, ...){va_list args;va_start(args, format);__android_log_vprint(ANDROID_LOG_VERBOSE,

"my_native_code", format, args);va_end(args);

}

__android_log_assert("0 != errno", "my_native_code", "Big error!");


Log Control

Cannot suppress log messages based on priority Preprocessor based solution

#define MY_LOG_NOOP (void) 0 #define MY_LOG_PRINT(level,fmt,...) \

__android_log_print(level, MY_LOG_TAG, \"(%s:%u) %s: " fmt, __FILE__, __LINE__, \__PRETTY_FUNCTION__, ##__VA_ARGS__)

#if MY_LOG_LEVEL_WARNING >= MY_LOG_LEVEL# define MY_LOG_WARNING(fmt,...) \

MY_LOG_PRINT(ANDROID_LOG_WARN, fmt, ##__VA_ARGS__)#else# define MY_LOG_WARNING(...) MY_LOG_NOOP#endif


Log Control

In native code

In Android.mk

#include "my-log.h"...MY_LOG_WARNING("Message!");

MY_LOG_TAG := \"my_native_code\“

ifeq ($(APP_OPTIM),release)MY_LOG_LEVEL := MY_LOG_LEVEL_ERROR

elseMY_LOG_LEVEL := MY_LOG_LEVEL_VERBOSE

endif

LOCAL_CFLAGS += −DMY_LOG_TAG=$(MY_LOG_TAG)LOCAL_CFLAGS += −DMY_LOG_LEVEL=$(MY_LOG_LEVEL)


Log Console Messages

STDOUT and STDERR not visible by default Redirect STDOUT and STDERR to logging system

Display with logcat - tags stdout and stderr Temporary config -> erased when booting device

Permanent config -> modify /data/local.prop on device

adb shell stopadb shell setprop log.redirect-stdio trueadb shell start


GDB

NDK supports debugging using GNU Debugger (GDB) ndk-gdb script

Handles error conditions Outputs error messages

Requirements Use ndk-build -> build system generates files needed for

debugging android:debuggable in AndroidManifest.xml Android version 2.2 or higher


Debug Session Setup ndk-gdb script sets up the debug session Launches the app using activity manager through ADB

Activity manager sends the request to Zygote Zygote forks and creates new process

ndk-gdb starts GDB server and attaches to the app Configures port forwarding to make GDB server

accessible from the host machine (debug port) Copies binaries for Zygote and shared libraries to the host Starts GDB client Debug session is active -> You can start debugging app

Commands sent over the debug port


Debug from CLI Make sure Eclipse is closed Go to project directory rm -rf bin obj libs Compile native code using ndk-build We need build.xml -> android update project -p Compile and package the whole project in debug mode ant debug

Deploy app on device ant installd ndk-gdb --start to start app and the debugging

session When GDB prompt appears run commands


GDB Commands break: Breakpoint in a location (function name, file name & line

number) clear: deletes all breakpoints enable/disable/delete: operations on a certain breakpoint next: go to the next line in source code continue: continue execution backtrace: display call stack backtrace full: call stack with local variables on frames print: display variable, expression, memory address, register display: continue printing value after each step info threads: list running threads thread: select a certain thread


DDMS Dalvik Debug Monitoring Server Debugging Android applications Port-forwarding, screen capture, thread info, heap info, process

state, radio state, incoming call, SMS spoofing, location spoofing, etc.

Integrated in Eclipse, tools/ddms (SDK) When started DDMS connects to adb VM monitoring service is created between adb and DDMS The service notifies DDMS when a VM is started or terminated Obtains the pid, opens a connection to the VM’s debugger

through adbd Talks to the VM using a custom wire protocol


DDMS

Source: http://developer.android.com


DDMS View how much heap the process is using

Select process in Devices tab Update Heap to obtain heap info Cause GC to invoke Garbage Collection (refresh data) Select object type to view number of allocated objects

Track memory allocation Start Tracking in the Allocation Tracker tab Get Allocations to obtain list of allocated objects Finally Stop Tracking Detailed info about the method and line that allocated a certain

object Examine thread info

Update Threads to obtain thread info for the selected process


DDMS - Heap Update



DDMS - Track Allocations



Stack Trace Use troubleshooting tools and techniques to identify the

cause of a problem Observe the stack trace when an app crashes with logcat Lines starting with # represent stack calls Line #00 is the crash point After #00 the address is specified (pc)

ndk-stack To add file names and line numbers to the stack trace adb logcat | ndk-stack -sym obj/local/armeabi Run command in the project directory Obtain exact file name and line number where it crashed


CheckJNI Extended series of checks before calling JNI functions Enable CheckJNI on a device

Rooted device

Logcat: D AndroidRuntime: CheckJNI is ON Regular device

Logcat: D Late-enabling CheckJNI

Error detected by CheckJNI

adb shell stopadb shell setprop dalvik.vm.checkjni trueadb shell start

adb shell setprop debug.checkjni 1

W JNI WARNING: method declared to return’Ljava/lang/String;’ returned ’[B’W failed in LJniTest;.exampleJniBug


Libc Debug Mode Troubleshoot memory issues Enable libc debug mode

Libc debug mode values 1 - detects memory leaks 5 - detects overruns by filling allocated memory 10 - detects overruns by filling memory and adding sentinel

adb shell setprop libc.debug.malloc 1adb shell stopadb shell start

... testapp using MALLOC_DEBUG = 10 (sentinels, fill)

... *** FREE CHECK buffer 0xa5218, size=1024, corrupted 1bytes after allocation


Valgrind Advanced memory analysis Open-source tool for memory debugging, memory leaks detection

and profiling Support for Android Build from sources

Binaries and components in Inst directory adb push Inst /data/local/ Give execution permissions

Helper script

Push in /data/local/Inst/bin and set execution permissions

#!/system/bin/shexport TMPDIR=/sdcardexec /data/local/Inst/bin/valgrind --error-limit=no $*


Valgrind

To run app under Valgrind, inject the script into the startup sequence

Property wrap.packagename Execute app Logcat displays Valgrind output

adb shell setprop wrap.com.example.testapp"logwrapper /data/local/Inst/bin/valgrind_wrapper.sh"


Strace

Intercepts system calls and signals System call name, arguments and return value Useful for analyzing closed-source applications Included in Android emulator Run the application and obtain pid

Attach strace to running app

adb shell ps | grep com.example.testapp

adb shell strace -v -p <PID>


Tombstones

Tombstone - generated when a process crashes /data/tombstones/tombstone_* A file containing information about the crashed process

Build fingerprint Crashed process, PID, TIDs Signal and fault address CPU registers Call stack Stack content of each call

Use with ndk-stack and addr2line to obtain the file and line where the process has crashed


TombstonesBuild fingerprint: 'Android/aosp_hammerhead/hammerhead:4.4.2/KOT49H/eng.upb.20140407.130154:userdebug/test-keys'Revision: '11'pid: 27836, tid: 27836, name: test.nativeapp4 >>> com.test.nativeapp4 <<<signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 00000000 r0 00000000 r1 00000000 r2 6f8b70e4 r3 6f8b8328[..]backtrace: #00 pc 00008bbc /system/lib/libandroid.so (AAsset_close+3) #01 pc 00000d47 /data/app-lib/com.test.nativeapp4-2/libNativeApp4.so (displayAsset(ANativeActivity*)+18) #02 pc 00000db1 /data/app-lib/com.test.nativeapp4-2/libNativeApp4.so (ANativeActivity_onCreate+96)[..]stack: bea91430 00000000 bea91434 401a7315 /system/lib/libutils.so (android::SharedBuffer::release(unsigned int) const+28) bea91438 bea91450 [stack] bea9143c 00000000 bea91440 00000000 bea91444 402ad59b /system/lib/libandroidfw.so bea91448 6f8b70e0 [anon:libc_malloc]


GNU Profiler (Gprof)

Unix-based profiling tool Compute absolute execution time spent in each function

Instrumentation with gcc when using -pg at compile time Sampling data stored at run-time in gmon.out gprof uses gmon.out to produce profiling reports

Android NDK includes gprof tool Android NDK toolchain lacks the implementation of __gnu_mcount_nc used for timing

Open-source project Android NDK Profiler


Android NDK Profiler

Install module Download zip, extract in $NDK_HOME/sources, rename

directory to android-ndk-profiler Enable profiler

Update Android.mk to statically link profiling library Include prof.h in the native code

#ifdef MY_ANDROID_NDK_PROFILER_ENABLED#include <prof.h>#endif


Android NDK Profiler

Start collecting profiling data

Stop collecting data

#ifdef MY_ANDROID_NDK_PROFILER_ENABLEDmonstartup("libModule.so");

#endif

#ifdef MY_ANDROID_NDK_PROFILER_ENABLEDmoncleanup();

#endif


Generate Reports The collected data is stored in /sdcard/gmon.out App needs permission to write on the SD card

Pull gmon.out from the SD card Run gprof

Gprof analyses data and generates a report Two sections: flat profile and call graph Duration of each function

<uses-permission android:name="android.permission.WRITE_-EXTERNAL_STORAGE" />

$NDK_HOME/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin/arm-linux-androideabi-gprofobj/local/armeabi-v7a/libModule.so gmon.out


Systrace Gather code execution data -> Identify execution

problems and improve performance Show all processes on a common timeline Execution times, CPU frequency, CPU load, disk activity,

threads Android 4.1 or higher, root access, developer debugging

enabled GUI and CLI

Open trace in a web browser

$ cd android-sdk/platform-tools/systrace$ python systrace.py --time=10 -o mynewtrace.html sched gfx view wm


Systrace - Analyze the Trace

Thicker bars (tasks that take longer than others) can indicate a performance problem



Systrace - Application Level Tracing

From Android 4.3 use Trace class to add instrumentation to the application code

Trace calls can be nested Traces must begin and end in the same thread

Trace.beginSection("Start trace");try {

// executing tasks} finally {

Trace.endSection(); // end trace}


Traceview

Graphical viewer for execution logs (generated with Debug class)

Timeline panel - displays each thread and method started/stopped

Profile panel - summary of all time spent in a method Two methods to generate trace logs:

Use methods of the Debug class to start and stop tracing Use method profiling feature of DDMS (no precise log timing)

Debug.startMethodTracing("data"); // start tracing to // "/sdcard/data.trace"

// execute tasksDebug.stopMethodTracing(); // stop tracing


Traceview - Timeline Panel

Displays the execution of each thread in a separate row Each method - a different color Thin line below - extent of all calls to the selected method



Traceview - Profile Panel All time spent in a method (inclusive and exclusive times) Exclusive time = time spent in a method Inclusive time = time spent in a method + time spent in any

called functions Last column - number of calls to this method + number of

recursive calls



Bibliography

Onur Cinar, Pro Android C++ with the NDK, Chapter 5, 14 Sylvain Ratabouil, Android NDK, Beginner’s Guide,

Chapter 11 https://code.google.com/p/android-ndk-profiler/wiki/

Usage http://developer.android.com/tools/debugging/

ddms.html http://bytesthink.com/blog/?p=133 http://developer.android.com/tools/debugging/

systrace.html


Keywords

Logger Logging API Log control GDB DDMS Stack trace Tombstones CheckJNI

Libc Debug Mode Valgrind Strace Gprof Android NDK Profiler Systrace Traceview

Lecture 7 - Debugging and Profiling

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Transcript of Lecture 7 - Debugging and Profiling